( 232 ) 



According to tliis formula one would l)c induced lo determine the 

 value of c from m and r, but it will appear in cliai)ter 6 that for 

 small tensions of the quartz-thread the virtual mass of the image 

 of the string is not a constant value. 



Hence it is not or iiardly possible to ileri\'e from measurements 

 that were performed with other tensions of the string, the value of 

 711 for the case that the limit of aperiodicity has been reached. And 

 if 111 is unknown c cannot be calculated, of course. 



So if one wants to know the sensitiveness for which the limit 

 of aperiodicity is reached, one is obliged to determine this directly 

 by experiment. The results of a number of such determinations 

 which, as will be understood, were only made in a rough way, are 

 found united in the following table VIII. 



From the data of the preceding table and from the \'alues of r 

 it would be possible to calculate the valnes of m. 



re 



Similarly those of the time-constant') T by the formula T = —. 



These calculations, however, nuist be omitted, since c has a far 

 too small degree of accuracy here, to attach any importance to the 

 results. 



TABLE YIII. 



Number 



of the 

 string. 



Sensitiveness c for the limiting 

 value of aperiodicity. 



with air-damp- 

 ing onlv. 



with air-damping 



and electro- 

 magnetic damp- 



5. The acceleration. 



When analysing a curve, recorded by the cat)illary electrometer, 

 if we wish to know the potential difference which at a certain 

 moment exists between the mercury and the sulphuric acid, we have, 

 besides the properties of the instrument and the speed of the recording 



1) See Fleming, I.e. pp. 377 IT. 



